Vault-plate



CHARLES MORRIS JOHNSQN, OF AVALON, PENNSYLVANIA.

' VAULT-PLATE.

be built. The object in View is flame resistance. In vault building steel of great hardness has heretofore been used, to resist the cutting tools employed by burglars; but such very hard steel is not sufliciently resistant to a blow-pipe flame, and in consequence such safes and the like which are strong to resist cutting tools may still be penetrated with relative ease, and the blow-pipe flame has become the burglars most effective tool. Under such conditions walls of safes and the like are now being built of compound plates or layers,some of these layers being hard to resist cutting tools, and others of softer material, more resistant to cutting by flame.

I have found through long continued study and experiment a steel mix, a steel alloy, which is in highest degree resistant to flame penetration, and my invention consits in a vault plate formed of such steel.

The steel alloy which I have worked out belongs in the class termed chrome steel: that is to say, it is steel alloyed with chromium. Chromesteel is not new with me;

nor is it new with me to use chrome steel for the walls of safes; the flame-resisting property of chrome steel as a class is known-though the reason why chrome steel is flame-resisting has not, so far as I am aware, been known heretofore. I have discovered the reason to be this: Chromium :oxid, which under the blow-pipe flame soon only but with nic el too,has a flame-re- Specification of Letters Patent.

' Patented June 8, 192d.

1919. Serial No. 315,960%.

sisting capacity exceeding the simple chome steel alloy, and furthermore, is workablecapable of being forged and sheared, drilled, and machined, etc.with an ease not enjoyed in the case of the simple alloy. Indeed, an obstacle to making plates of s mple chrome steel has been the impossibillty of fabricating, if the chromium con tent be great. For attaining the object now in view, I find that, within the range of my experiments, the greater the chromium content the greaterthe capacity to resist flame penetration. I further find that by adding nickel to the alloy, not only do I remove the obstacle mentioned,-or, rather, push it farther out of the path,but that, instead of impairing the capacity to resist flame (a result which might have been expected), I actually improve that capacity. So I obtain a new result, a steel of great flame-resisting quality which is easily workable, a vault plate which reveals a flame-resisting capacity unapproached by anything heretotofore devised.

The characteristics of my vault plate material are these: First of all, it is a steel compounding of some of which the inclusion of small quantities of chromium has been proposed. Fourth, the chromium ingredient ranges from 10% upward, accompanied with a nickel ingredient of 2% and upward. The upper limit to the amount of chromium is still the point at which the steel ceases to be workable, or (more corhrectly statedl thepoint at which the cost of production forbids going higher. An alloy 15%, showed under test flame-resisting 106 containing chromium 25%, with nickel I The range of preferred composition under existing limitations upon mill operation is, chromium, to 25%, nickel, 2 to v The carbon low; otherusual adulterants and metalloids present in small percentages in various steels, are in their presence or absence unrelated to the present invention. That is to say, the invention may be=practised upon steel of varying character and quality, so far as concerns these adulterants. 1

It further appears that the steel of my invention is in-markeddegree resistant of attack by acid; it is then in the category of This quality further stainless. steel.

adapts it to use not only for the heavy protecting walls of safes, etc., but also for forming the lighter partitions" and safe deposit boxes and drawers within; for the parts made of this material may be kept bright,-even under diflicult atmospheric conditions. And the bright and clear appear ance of such structure is a not inconsiderable matter.

The particular way in which my improved vault plate "is built into the safe structure, or the particular manner it may content of the steel should be of my present invention. v

. I claim as my invention:

1. A vault plate formed of a nickel-'v chromium-steel alloy, in which the chromium content is at least l()%," subs'tantially as described. 1

2. A vault plate formed of a nickelum content is at least 10% and the nickel content at least 2%; substantially as described. I

3. A vault plate formed of a nickelchromium-steel alloy, in which chromium is between 10% and 25% and nickel between 2% and 15%, substantially as described.

4. A vault plate formed of a nickelchromi'um-steel alloy, in which steel is the dominant component and the chromium content is at least 10%, substantially as described.

In testimony whereof I have hereunto set my hand. a

CHARLES MORRIS JOHNSON.

Witnesses: v

B'AYARD H. Cnnrs'rr, FRANCIS J. TOMASSON.

chromium-steel alloy, in which the chronii- 

